The present invention relates to a method for whitening teeth. More particularly, the present invention relates to a method for whitening teeth which utilizes laser light to activate bleaching agents.
Development in the field of teeth whitening has led to the presently used method of xe2x80x9cpower bleaching,xe2x80x9d which is generally described as follows. A rubber sheet or dam is placed over the patient""s teeth so that the teeth protrude through the sheet. The dam is made from latex rubber forced over each tooth and held in place with metal springs, clamps, and ligatures. This partially protects the soft tissues of the gums from the peroxides used in bleaching. However, since the rubber sheet stretches and does not custom fit the particular patient""s mouth, the peroxide can leak around the rubber sheet and cause substantial discomfort to the patient. Typically, this method can be performed only on the upper or lower set of teeth at a time, not both.
Once the rubber sheet is in place, a peroxide solution is coated on the teeth. Since the bleaching effects of peroxide are slow, the common practice is to apply heat to the peroxide to accelerate the reaction. This is accomplished with the use of a heat lamp or heating iron. Although the heat accelerates the bleaching process, a substantial amount of time is still required so that the entire bleaching process must be performed over several appointments, resulting in inconvenience, time loss, and substantial expense.
The heat lamp activates the peroxide on a plurality of teeth simultaneously but, due to the amount of heat required where heat is the sole means for activating the peroxide, also exposes the patient""s face to significant amounts of heat, which is quite uncomfortable and cannot be endured for a prolonged period. While the heating iron does not expose the patient""s face to the same extent as the heat lamp, it takes a much longer time to perform the whitening since it affects only one or two teeth at a time. In addition, prolonged exposure to heat will increase the temperature of the pulp within the tooth, causing discomfort to the patient if the pulp temperature gets too high. Since the amount of heat commonly used in this type of procedure could kill the pulp and cause tooth loss if exposure is prolonged, continuous exposure must be limited. As a result, 2 to 5 office visits are required before adequate bleaching is attained.
Other prior art tooth bleaching techniques utilize both light and chemical activation of hydrogen peroxide to accelerate the bleaching process. For example, in Toh, C. G., xe2x80x9cClinical Evaluation of a Dual-activated Bleaching System,xe2x80x9d Asian Journal of Aesthetic Dentistry, Vol. 1, No. 2, pp. 65-70 (July 1993), a powder containing potassium persulphinate (sold under the name xe2x80x9cOxonexe2x80x9d by the DuPont Corp.) was mixed with solutions of hydrogen peroxide to form a paste. The paste was applied to discolored teeth and activated using a dental curing light. Two different concentrations of hydrogen peroxide were usedxe2x80x9419% and 35%. A similar process is disclosed in U.S. Pat. No. 5,032,178, which also mentions the use of a 30-35% aqueous solution of hydrogen peroxide, with Oxone as an accelerator, and a dental curing light.
The described use of the laser whitening method of the present invention has certain advantages over the use of dental curing lamps and the like. For example, heat lamps designed for tooth whitening, such as the Union Broach Illuminator, utilize halogen bulbs which are significant sources of yellow light. However, because the pulp tissue in living teeth is red, it rapidly absorbs the yellow light causing it to rise in temperature, resulting in patient discomfort. A similar problem arises with incandescent bulbs. Like halogen bulbs, they produce all wavelengths of visible light, much of which is absorbed by the tooth pulp.
Also known in the art is the use of a laser in combination with hydrogen peroxide to bleach teeth. For example, Spanish patent application no. ES 528007, in the name of Vicente M. Torres Zaragoza, generally discloses the use of laser radiation to accelerate the bleaching action of hydrogen peroxide, but does not disclose a specific type of laser or method of using a laser to accelerate bleaching. Unlike curing lights, lasers permit the practitioner to expose selected teeth to a focused beam of light, thereby concentrating the energy of the beam where it is needed.
From the foregoing it may be seen that there remains a need for a method of whitening teeth which better protects the soft tissues, shortens the time for the procedure, and reduces the discomfort to the patient.
In accordance with the principles of the present invention, the use of the light source of the described laser permits the practitioner to choose the specific wavelength of such light that will be most effective in eliminating the particular stain. It is advantageous to select a wavelength close to the color of the stain to be bleached so that the light will be absorbed primarily by the stain molecules rather than the tooth pulp.
It is the object of the present invention to provide a method for whitening teeth that improves upon prior art methods and substantially reduces discomfort to the patient.
It is another object of the present invention to provide a method which can be performed within a short period of time, requiring only one office visit in most cases.
These and other objects of the present invention are accomplished through a method which utilizes laser light from an argon ion laser to activate bleaching agents applied to the teeth. The mouth is first prepared so that the soft tissues of the gums are protected and only the teeth are exposed. This is preferably accomplished using wax-like strips applied to the gums to isolate the gums from the chemical bleaching compounds. Typically, prior to a bleaching treatment, the teeth are cleaned to remove any materials which may reduce or nullify the effects of the bleaching agents. A mixture of peroxide is prepared and applied to the teeth. The teeth are then exposed to laser light from the argon laser to light activate the peroxide and accelerate the bleaching process.
In alternate embodiments of the invention, xe2x80x9cboostersxe2x80x9dand catalysts are used to further accelerate the bleaching process. Boosters are chemical compounds that, like hydrogen and carbamide peroxide, decompose into free oxygen radicals and thereby increase the effectiveness of the bleaching compound beyond that of the hydrogen peroxide alone by boosting the free oxygen radical concentration. A catalyst is any substance that causes a change in the rate of a chemical reaction without itself being consumed by the reaction.
In a preferred method of the present invention, a first bleaching step utilizing peroxide, light activated with an argon laser, is followed by a second bleaching step also utilizing peroxide, heat activated using a carbon dioxide laser.
These and other objects and advantages of the invention will become apparent from the following detailed description of the invention.